Fix issue with incorrect migrations in SequelizeMeta getting deleted when reverting

This fixes two scenarios (tested in PostgreSQL and SQLite):

1) When performing one off migrations using ```sequelize -m``` after each new migration if you revert a migration using ```sequelize -m -u``` the earliest record in the SequelizeMeta table gets deleted instead of the latest record (which corresponds to the reverted migration).

2) When performing multiple migrations using ```sequelize -m``` if you revert the multiple migrations using ```sequelize -m -u``` the earliest records in the SequelizeMeta table get deleted instead of the latest records (ie if 2 migrations were reverted the earliest 2 will be deleted instead of the last 2 corresponding to the reverted migrations).

Both of these scenarios are apparent when trying to run ```sequelize -m``` again after ```sequelize -m -u```  to re-run the reverted migration(s) since the SequelizeMeta table shows the latest script has been run.